The Spitzer administration announced the settlement of all insurance claims at ground zero yesterday, ensuring that $4.55 billion will be available for rebuilding the World Trade Center site. The agreement, which the insurers described as the largest single insurance settlement ever undertaken by the industry, ended a protracted legal battle with insurers over payouts related to the terrorist attack. New York State and Port Authority officials said yesterday that the deal removed any uncertainty over how much money would be available for rebuilding and would enable them to obtain private financing for the $9 billion project.